In oil and gas applications, fluids are frequently injected into a wellbore for a variety of different purposes and various types of surface pumps are employed. In prior art, a multistage centrifugal pump could be mounted horizontally, at the surface, adjacent to, or nearby the well requiring fluids to be injected into, and current designs have a maximum discharge pressure of 6,000 psi. This multistage centrifugal pump is one type of pump that is most often used in a vertical configuration within a wellbore for pumping fluid from the well to surface pipeline systems, as a production pump, and current designs have a maximum discharge pressure of 6,000 psi. In the oil and gas industry, which utilizes fracing operation to simulate Oil and Gas reservoirs, this operation requires high surface fluid treating pressures, which may be 10,000 psi. The present invention, a high pressure multistage centrifugal pump, has been designed to increase the operating discharge pressure from 6,000 psi to 10,000 psi to enable this pump to meet the above described application. This high discharge pressure capability could also be applied to other applications too.
The prior art multistage centrifugal pump is used in the Electric Submersible Pumping System (“ESPS”) industry or in its surface Horizontal Pumping System (“HPS”) application, which are limited to discharge pressure or differential pressure between internal and external pressure of the housing, to be below 6000 psi. The o-rings are commonly used as a sealing element between an intake and a pump base as well as between a discharge and a pump head. The diffusers contain the pressure generated in the pump stages and the pump housing is only used as secondary pressure containment since its primary role is to hold pump components together. The pump housing is sealed with o-rings on a pump base and a pump head. Diffusers are not designed to withstand high differential pressure between the outside and inside of the diffuser.
U.S. Pat. No. 3,861,825 teaches a multistage pump and manufacturing method. It describes the split-casing style of centrifugal pump. The pump speed is listed as approximately 12,500 rpm, with a discharge pressure that may be 2600 psi, with a suction pressure of 15 to 30 psi. They do reference previous patents, and then list some patents that have similarities.
The pump Nexen has disclosed herein is a housing type of centrifugal pump, operating at speeds of 30 to 90 hz, (1800 to 5400 rpm), with discharge pressures that may be 10,000 psi, and with a suction pressure that may be 15 to 600 psi. Any similarities would be with respect to centrifugal pumps in general, and the fact that they are composed of multiple stages.
U.S. Pat. No. 5,232,342 teaches high pressure multi-stage centrifugal pumps. It describes the split-casing style of centrifugal pump. That invention relates to means for preventing rotation of an interstage bushing or ring, as the main objective. There is no reference in this patent as to the discharge pressure capabilities to go along with the “High Pressure” referenced in the heading.
The pump Nexen has disclosed herein is a housing type of centrifugal pump, which is designed for operating at speeds of 30 to 90 hz, (1800 to 5400 rpm), with discharge pressures that may be 10,000 psi, and with a suction pressure that may be 15 to 600 psi.
The main difference here is we are using a housing type of centrifugal pump and are building it with many more stages than what has been done in the past. The pressure capability far exceeds current design standards (6,000 psi maximum listed by other manufactures such as Reda, Centrilift, Woodgroup, Weatherford, Canadian Advanced Inc.). Canadian Advanced ESP Inc. (“CAI”) states in their HPS brochure that the HPS Design Capacities are maximally 4600 psi. CAI used special construction techniques to meet Nexen design and specification requirements to accommodate the high discharge pressure capabilities of 10,000 psi heretofore unknown.
With these ends in mind the main objective of the present invention is to provide details on pump construction that was used to expand the multistage housing centrifugal pump to enable it to operate at a very high discharge pressure of 10,000 psi. The high pressure is contained by the housing, which the diffusers are inserted into. High pressure is controlled through the use of seals on the external of the diffusers to prevent cross flow to other diffusers. Openings in external wall of diffusers are used to provide rapid release of pressure trapped between the diffusers and the housing to prevent diffuser collapse when a unit is shut-down and depressurized. One skilled in the art would appreciate the modifications provided in the present invention to achieve its objectives i.e. sufficient pressure control and pressure relief for the diffuser as required. This pressure release could be accomplished by slots, holes and other openings.
Special threading on the discharge ends of housings is required to support high pressure pipe connections.
It is yet another object of the invention to provide a multiple stage centrifugal pump for fracturing hydrocarbon deposits that is capable of generating in excess of 10,000 psi.
It is a further object of the invention to provide said pump designed to equalize pressures in the housing of said pump from stage to stage.
It is another object of the invention to provide said multiple stage centrifugal fracturing pump with construction materials in alignment with the well known recommendations published for material performance criteria from for example, NACE (National Association of Corrosion Engineers), ASTME (American Society of Tool and Manufacturing Engineers) or ANSI (American National Standards Institute) trim packaging or the like in view of the corrosive nature of the fluids being pumped.
It is another object of the invention to provide said pump with the preferred NACE trim packaging or the like in view of the corrosive nature of the fluids being pumped.
It is yet another object of the invention to provide a multiple stage high pressure centrifugal pump capable of use in fracturing a hydrocarbon reserve while avoiding treating the aquifer water prior to using it for hydrocarbon fracturing as a result of the high pressure capabilities of said pump.
It is a further object of the invention to enable the use of non-potable underground aquifer water, such as the Debolt formation aquifer, as a source of water for the fracturing of underground rock formations containing hydrocarbon reserves.
Further and other objects of the invention will be apparent to one skilled in the art when considering the following summary of the invention and the more detailed description of the preferred embodiments described and illustrated herein along with the appended claims.